Spread butter on both sides of bread. Layer bread, cheese, mushrooms, and bacon 1/2 at a time in a 9 by 13 baking dish. Combine remaining ingredients in a bowl, mix until smooth and pour over layers. Chill overnight. Bake casserole for 1 hour at 325 degrees. Let stand for 15 minutes before serving.

We loved this with GREEN CHILIES....verry good, we also love this with breakfast sausage with the bacon! Yummy. Substitute is easy with this recipe.